The right hemispheric dominance for faces in preschoolers depends on the visual discrimination level.

The developmental origin of human adults’ right hemispheric dominance in response
to face stimuli remains unclear, in particular because young infants’ right hemispheric
advantage in face-selective response is no longer present in preschool children, before
written language acquisition. Here we used fast periodic visual stimulation (FPVS)
with scalp electroencephalography (EEG) to test 52 preschool children (5.5 years
old) at two different levels of face discrimination: discrimination of faces against objects,
measuring face-selectivity, or discrimination between individual faces. While
the contrast between faces and nonface objects elicits strictly bilateral occipital responses
in children, strengthening previous observations, discrimination of individual
faces in the same children reveals a strong right hemispheric lateralization over the
occipitotemporal cortex. Picture-plane inversion of the face stimuli significantly decreases
the individual discrimination response, although to a much smaller extent
than in older children and adults tested with the same paradigm. However, there
is only a nonsignificant trend for a decrease in right hemispheric lateralization with
inversion. There is no relationship between the right hemispheric lateralization in
individual face discrimination and preschool levels of readings abilities. The observed
difference in the right hemispheric lateralization obtained in the same population of
children with two different paradigms measuring neural responses to faces indicates
that the level of visual discrimination is a key factor to consider when making inferences
about the development of hemispheric lateralization of face perception in the
human brain.